Navigation system

ABSTRACT

A navigation system for determining on board a moving craft the position of the moving craft in relation to a fixed station which is provided with visual means for guiding said moving craft wherein there are means on said station for visible said visual means to the navigator of said moving craft by means of laser beams.

United States Patent 1191 Brosow 1 Jan.8,1974

' [76] Inventor:

1 NAVIGATHON SYSTEM Jorgen Brosow, Haekspettragen l3, Bromma, Sweden[22] Filed: May 27, 1971 [21] Appl. No.: 147,410

[30] Foreign Application Priority Data May 29, 1970 Sweden 7415/70 52us. c1. 340/25, 244/114, 343/108 M 151 1111. e1 G08g 5/00 [58] 10010 ofSearch 340/22, 25, 26, 27 R, 340/27 AT, 28, 27 NA; 250/199, 331/945 A;343/108 R, 108 M, 5 LS; 240/12;

[56] References Cited UNITED STATES PATENTS 3,710,098 l/l973 Walden340/25 3,671,963 6/1972 Assouline et al. 340/27 NA 3,657,792 4/1972 Huget al. 350/7 3,648,229 3/1972 Burrows et al 11 340/26 3,370,269 2/1968Jasper 340/22 3,527,949 9/1970 Huth et al 250/199 3,447,129 5/1969Birmingham et al. 340/26 3,293,438 12/1966 Davis, Jr 1. 250/1993,279,406 10/1966 Ricketts et 31.. 340/26 3,227,882 1/1966 Bissett eta1. 250/199 3,139,604 6/1964 Meiners et al 340/25 3,138,779 6/1964Murray, Jr. et aL... 340/25 2,989,727 6/1961 Germeshausen 340/26 PrimaryExaminer-William C. Cooper Assistant Examiner-Randall P. MyersAtt0meyHammond and Littell [57] ABSTRACT A navigation system fordetermining on board a moving craft the position of the moving craft inrelation to a fixed station which is provided with visual means forguiding said moving craft wherein there are means on said station forvisible said visual means to the navigator of said moving craft by meansof laser beams.

2 Claims, 5 Drawing Figures PAIENTEQJAM 8 I974 sum 3 or 3 FIG.4

NAVIGATION SYSTEM THE FIELD OF THE INVENTION The present inventionrelates to a navigation system for determining on board a moving craftthe position of said moving craft relative to a fixed station equippedwith visual means for guiding the moving craft. The object of theinvention is to improve the reliability of such systems, particularlyduring the approach and landing of moving craft on such runways which(in each particular instance) are marked by runways indication devicespositioned remote from and close to the runway. The system of theinvention renders unnecessary the use of such illuminating devices asfloodlights etc. and provides for a longer viewing range than previousnavigation systems, particularly in bad weather conditions. Furthermore,the navigation system of the present invention renders discovery ofairfields and landing strips by pilots of aircraft other than those tobe accomodated thereon more difficult.

A navigation system of the present invention is mainly characterized bymeans arranged on the fixed station for making visible to the navigatorof the move craft by means of laser means the visual guiding meansarranged on said station. These means include reflecting screens which,when practicing the invention, become sequentially visible to the pilotof an aircraft, for example, to enable a safe landing to be made on aspecific runway of an airfield. The laser beams can be swept in thevertical plane to render the screens visible from the level of theground up to a certain upper limit height angle. Other series of laserbeams can be used which sweep in the horizontal plane within adetermined sector. The beams can be swept at a uniform speed, eitherwith an intermittent movement or with a reciprocating movement,optionally with a reciprocat ing movement of small angular amplitudesuperposed on a smooth movement. For the sake of safety, it is suitablethat the beams are only active within the angular regions required ineach particular instance. The.

screens are erected one behind the other at suitable intervals,preferably in a straight line. The screens are also provided with meansfor regulating the reflection angle of the reflected beams, for examplewhen the laser beams are swept vertically, so that said angle is thesame for all screens and coincides with the aforementioned limit heightangle. Each screen may be in the form of a box provided with aperforated front wall to enable the laser beams to penetratetherethrough and impinge on individual, adjustable reflecting devicesarranged in the box behind respective apertures. The laser beams areswept by means of rotating or rocking prisms or mirrors arranged in thelasers and the beams are dimmed in a manner whereby the projected beamsare in the form of strips of light. If several lasers ar used, they maybe arranged so that laser beams of different colors are obtained. Inthis way it is possible to obtain a series of screens which is actedupon by a laser which radiates a certain color, while one or more otherseries of screens are acted upon by beams of one or more other colors.This is a suitable expedient if the screens are to indicate boundariesfor different ground areas.

If the navigation system is to be used to facilitate the landing of anaircraft, a first series of screens may be used to mark the approachline of the runway with one particular color, for example yellow, andanother series of screens positioned to the left of said first seriesand a further series of screens positioned to th right of the firstseries with the screens placed along left and right, suitably converginglines may be used to indicated the boundaries of an interception sectoror an approach sector tapering in towards the runway.

To enable coded information to be transmitted from the field station to,for example, an approaching aircraft, the laser beams can be reflectedas reflex modulated beam from their source.

The invention will now be described in more detail with reference to anembodiment thereof illustrated in the accompanying drawings.

FIG. 1 is a diagrammatic, greatly compressed side view of an embodimentofa navigation system for guiding aircraft to the runway of an airfield.

FIGS. 2 and 3 show in perspective and in section a reflecting screen inthe form of a box.

FIG. 4 is a top plan view of a landing navigation system constructed inaccordance with the invention for indicating the direction of approachto the aircraft and also showing the boundaries of a permitted approacharea, for the purpose of directing aircraft from remote distances to thescreens which mark the approach direction.

FIG. 5 illustrates a code modulation system embodied in the navigationsystem of the present invention.

In the embodiment of FIG. 1, laser beams are generated from a laser 1situated within a housing 4 having a departure opening 5 for a laserbeam I3. Laser beams from the laser l are dispersed through a lens 2 andreflected by a rotating prism or mirror 3, which is rotated in thedirection of arrow 12, and pass through the opening 5, which is of suchconfiguration that a strip-like beam 13 is projected towards a series ofscreens 7. In the illustrated embodiment the screens 7 are positionedone behind the other along a straight line. The reference numerals 6 and15 indicate an upright and a frame structure for the housing 4 and thescreens 7 respectively. The screens are box-shaped (as is best seen fromFIG. 3) and are arranged at a level above the ground higher than theheight of a man. The angle of the screens can be adjusted in relation tothe surface of the ground and in the illustrated embodiment the screensare of the same height. The beams 13 are projected from a point which isconsiderably higher than the screens 7. A conceivable distance betweenthe screens is 50 meters. The beam 13 is swept from the bottom of thescreen upwardly and impinges on the screens 7 in sequence, from thefront screen and moving rearwardly, and can make the screens visibleeither one at a time or several at once. If the beam 13 is also used totransmit information, it can suitably be caused to remain stillmomentarily on, for example, the last screen.

the only beams present at a certain moment and that said beams, duringthe sweep, successively adopt the illustrated positions up to boundarypositions for the reflected beam 43. In the illustrated embodiment, theincident beam is restricted by the upper and lower edge surface of theopening 5 and is caused to be projected within the area between thebeams 13 and 44, while the reflected beam is maintained within theboundaries defined by the beams 14 and 43.

As is evident, the capacity to make of the reflected beams visible isrestricted to the angle of elevation 04 and that consequently thescreens 7 are not visible to aircraft flying in an area above saidangle. It has been assumed in the aforegoing that the beam is sweptsmoothly towards the screens from the bottom thereof upwards, optionallywith a certain stationary period at the last screen. However, thesweeping movement can be superposed with an oscillating movement orfluttering movement effected by means of such a movement caused by theprism 3 for example. Furthermore, the beam may be caused to remain for aspecific length of time on each screen, or a stationary beam may befixedly directed against the last screen 7. One embodiment of a screenis illustrated in FIGS. 2 and 3.

Other screen designs, for example screens in the form of a grid, may besuitable in certain cases, e.g., to prevent the reflection ability ofthe screens from being reduced by adhering snow.

The illustrated screen 7 is box-shaped, having aperture 8 disposed inthe end wall thereof facing the laser. In the embodiment illustrated inFIG. 3, each aperture cooperates with an individual mirror 9, which canbe adjusted by means of an actuator 16 and a sighting scale 10 locatedin the aperture 8 for setting the reflec tion angle a. The incident beamis identified by the reference numeral 13 and the reflecting beam by thereference numeral 14, as in FIG. ll.

FIG. 4 is a top plan view of a more complicated aircraft approachsystem. It is emphasied that this embodiment is concerned with the closeapproach of the aircraft at the landing stage and that direction ofaircraft at remote distances is effected in a conventional manner, e.g.,with the assistance of radio. The illustrated system replacesconventional light beams and landing lights normally found in airfieldnavigational systems.

A runway 28 is provided with a number of screens 7, which mark thecenter line of the runway. When sweeping the beam 13 vertically, thesemarkings becomes visible to aircraft located within the range of thereflected beams, but only if the aircraft is flying beneath theelevation angle limit at. These markings are, on the other hand, notvisible from a point of observation directly above the same. Because ofthis and because the laser beams are not illuminated until theapproaching aircraft is ready to land, the possibility of the airfieldbeing discovered by enemy aircraft, for example, is considerablyreduced, which plays an important part in times of war. Furthermore, theeffect of the laser beams is not influenced by poor weather conditionssuch as fog. As previously mentioned, the screens 7 are acted upon bythe beam 13 from the laser, which is a composite laser having a greenradiating portion 1 and a red radiating portion 17, wherewith thesecolors are combined to form a yellow beam 13. Consequently, the centerline of the runway is marked by yellow reflecting beams.

To the left of the laser 1, 17 in the drawing is a blue radiating laser18, the beam 19 of which is divided by a prism 25 into a through-passingbeam 20 and a beam 19 which is reflected towards a rotating mirror 3 bya mirror 26, the mirror 3 operating as previously described to sweepover a series 23 of reflectiondependent screens 21 situated to the leftof the screens 7 in figure. The screens 21 are arranged along a lineinclined to the path 28, whereby a sector between the series 23 and thescreens 7 is marked with a blue color.

The beam 19 reflected through is projected against a rotating prism 27,which in turn reflects the beam 19 towards a series 24 of screens 22situated to the right in the drawing. The series 22 is arranged tofunction analogously with the lefthand series 23. The final result is ablue approach sector which tapers towards the runway and which isvisible at greater distances than the beams from the screens 7.

Other colors can be used to obtain starboard and port marking of theapproach sector, e.g., red and green marking. In the illustratedembodiment either one or both of the vertically or horizontally sweptbeams may have a superposed fluttering movement, while in other respectsthe aforementioned intermittent sweep may also be used.

One example of the manner in which a sweep can be effected is one inwhich one sweep is made per second, i.e., the laser beam is able toactivate during this period all screens, for example 20, in I second,which means that each screen is illuminated for 50 milliseconds.

FIG. 5 illustrates an example for a communication system for codedcommunication between the ground station and the approaching aircraft.

A laser 1 projects a beam 13 against a mirror 37. The mirror projectsthe beam against a tuning fork 37 oscillated, for example, by theoscillator 33 and provided, for example, with a hard chromium reflectingsurfaces. The oscillator causes the fork 29 to oscillate at a frequencyof, for example, 900 p/s.

The beam, modulated to the aforementioned frequency, is then passed fromthe fork 29 successively to the mirror 38, the mirror 39, the mirror 40and the mirror 41 by forks 30, 31, 32 driven by oscillators 34, 35, 36at forced oscillating frequencies b, c, d against the rotating or fixedmirror or prism 42, to be then directed against the reflectors (notshown). The frequences, b, c, d can be, for example, 600, 1,200 and 300p/s.

According to the desired coding, combinations of the frequences can beemployed to modulate the beam 13. In the illustrated embodiment allforks are shown to oscillate so that the beam is successively modulatedwith the frequencies a d and finally to obtain all said frequences(a+b+c+d). It is obvious the coded laser beams can be used forcommunicating with an aircraft both with landing and take-off. In thisinstane the aircraft should be provided with a receiver, e.g., havingphotocells which can receive the code frequency combination ofreflection modulated laser beam 13.

The invention has been described with respect to special, non-restrictedembodiments. It will readily be perceived that the navigation system ofthe present invention affords considerable improvements in such systemsfor approach and landing of aircraft, although these improvements cannot be completely taken up in this application because of reasons ofspace. It will also be understood that the drawings only illustrate theprinciples of the navigation system in a very simplified form and thatconsequently one of normal skill in the art for sweeping a first laserbeam in a vertical plane along said first array, means for sweepingsecond and third laser beams along said second and third arrays,respectively, and means for restricting the visibility of the beamsreflected by said screens to predetermined angu lar sectors in thevertical and horizontal plane, respectively.

2. A navigation system according to claim 1, wherein said threeegenerated laser beams are beams of different colors.

1. A navigation system for visually aiding a pilot in landing anaircraft, comprising a first array of laser beam reflecting screenslocated sequentially along a straight line pointing towards a runway, asecond and a third array of laser beam reflecting screens located on theright hand and left hand side, respectively, of said runway and mutuallyconverging towards said runway, means for generating stripshaped laserbeams, means for sweeping a first laser beam in a vertical plane alongsaid first array, means for sweeping second and third laser beams alongsaid second and third arrays, respectively, and means for restrictingthe visibility of the beams reflected bY said screens to predeterminedangular sectors in the vertical and horizontal plane, respectively.
 2. Anavigation system according to claim 1, wherein said threee generatedlaser beams are beams of different colors.